Bangladesh adjoins the Asian region with the severest AIDS epidemic and has common borders with two of the most affected areas, the Indian Hill States and northern Burma. There has been disagreement about the danger to Bangladesh, one view citing the likelihood of transmission from neighbouring infected populations and the other claiming that the country's predominantly Muslim culture protects it. This paper reports on a 1995-1997 research project. Preliminary research was carried out in Dhaka in 1995-1996 which suggested that the poor squatter areas might well sustain an epidemic. The experience also showed that more accurate measures of sexual networking could be obtained from males than females. The 1997 field research reported here investigated 983 males, 52% single and 48% married in Chittagong city and two more rural areas of Chittagong Division in southeast Bangladesh. It was found that around half of all males and probably a somewhat lower proportion of females, experience premarital sexual relations, with males having a lower level of extramarital than premarital relations. The factor heightening Bangladesh's risk of an epidemic is that one-quarter of single males and a significant but lower level of married males have had relations with prostitutes. This is one explanation for quite high levels of STDs in Bangladesh. The factors restricting the chances of a major national epidemic are the small number of premarital sexual episodes per person and the low level of intravenous drug use.